Abortion has been steadily increasing almost from the moment it was legalised 40 years ago - one of many reasons why it still stirs up controversy.

In 1968, the first year after abortion was legalised, just over 22,000 terminations were carried out - in 2006 the figure in England and Wales exceeded 193,000 a year.

The 1967 Abortion Act spells out the categories under which a termination can be permitted.

The figures on these categories tell us only a fraction of the human stories that lie behind the decision to have an abortion.

Just 1% are on the grounds that the child born would be seriously disabled and only 2% are because the pregnancy would affect existing children in a family.

It is not satisfactory that the rate of abortion is partly caused by people using it as a form of contraception

Lord Steel

The vast majority - 96% - are because of injury to a woman's health - a broad category which covers almost every cause of an unwanted pregnancy.

These figures have prompted a debate about whether abortion is being used as contraception.

The man who proposed legalising abortion 40 years ago accepts that is sometimes the case.

Lord Steel said: "It is not satisfactory that the rate of abortion is partly caused by people using it as a form of contraception.

"But it is important to note that the level of abortion in this country is still significantly lower than it is in some other countries like Australia and the US."

Some of Lord Steel's concern is shared by the Royal College of Obstetricians and Gynaecologists - it argues that there needs to be rethink of the way sex education is provided, with the aim of changing attitudes and behaviour.

The taboo, even 40 years on, is really strong

Dr Kate WorsleyMarie Stopes International

While unwanted teenage pregnancies remain a concern in the UK, almost half of all abortions are carried out on women in their 20s and the overwhelming majority of terminations are before 13 weeks gestation.

The 1967 Abortion Act does not apply to Northern Ireland, where abortion is only legal under some limited conditions.

Overall, 32% of women having an abortion will already have had at least one termination and nearly half will already be mothers.

Forty years on and surprisingly little is known for certain about the many reasons which lead women to seek an abortion.

Dr Kate Worsley, of Marie Stopes International, said in her experience most women were very clear about their decision.

She says the rising number of abortions is a failure of contraception - with it either letting women down or being used inappropriately.

Social taboo

Although she supports women's right to chose, Dr Worsley accepts there is still a strong social taboo that prevents many women from disclosing abortions to their close friends, family and partners.

Young people are much more aware of what abortion is, and how traumatic, and how drastic it is

Anne Atkins

"The taboo, even 40 years on, is really strong. It is such a personal and sensitive issue and I think women fear judgement still and fear that they won't be able to justify their decisions."

The debate about abortion has never really gone away but it fluctuates in intensity.

Medical understanding of the development of foetuses has moved on and the prospects for babies born very prematurely have altered beyond recognition.

Anne Atkins, a Christian commentator, argues growing knowledge has, if anything, led to a more ambivalent attitude.

"You no longer hear the sort of vocabulary that we heard 20 years that a foetus is just a blob of jelly, or part of a woman's body. You don't hear that kind of flippant talk anymore.

"Young people are much more aware of what abortion is and how traumatic and how drastic it is. That is not to say they won't take that option."

Doctors want reform

But some doctors now believe an abortion law 40 years old is more than due for an overhaul.

Next week the BMA will hear a call at its annual conference for abortion to be made easier for women in the early stages of pregnancy.

A motion calling for the need for two doctors to approve a termination to be reduced to one has gained the backing of the BMA ethics committee.

They also want a relaxation of the rules governing where it can be carried out, to allow pills to be dispensed in GP surgeries.

Even if the BMA were to support the move it could only happen with a change in the law - and that would inevitably prove controversial.